• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.506-513
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• 2020

In this study, the mechanical properties, absorption, and reduction performance of NOx in the mortar containing mineral admixture like zeolite and active hwangtoh were evaluated. Zeolite and active hwangtoh were used as binder, and zeolite and active hwangtoh were substituted for cement. The substitution ratio of two types of mineral admixtures was considered as 20 and 30% respectively. As a result of evaluating the compressive strength and flexural strength of each mortar specimen, the highest strength in the plain mixture was evaluated. As the substitution ratio of zeolite and active hwangtoh increased, the compressive and flexural strength decreased. In addition, the difference of compressive and flexural strength between active hwangtoh and zeolite mixing was evaluated to be insignificant. To evaluate the absorption rate, the mixture was designed to lower the W/B ratio of the existing mixture and set the substitution ratio of active hwangtoh and zeolite at 25%. The highest absorption ratio in the mortar with zeolite was evaluated, and the difference in absorption ratio between the remaining two mortar mixtures was small. The assessment of reduction performance of NOx considering the application of photocatalyst showed a clearly decreasing reduction behavior, even if they were the same mortar mixture. Zeolite and active hwangtoh also showed a higher NOx reduction than the Plain mixture, because of their porosity properties. In the case of active hwangtoh, the absorption ratio was lower than that of zeolite mixture, but the reduction of NOx performance was better than the result of zeolite mixture.

• Korean Journal of Food Science and Technology
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• v.23 no.4
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• pp.465-470
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• 1991

In order to investigate the thermal and oxidative stability of different frying oils including soybean oil, palm oil, two blended oils of soybean-palm (5 : 5 and 7 : 3) and shortening, physico-chemical properties such as acid value, peroxide value, TBA value, degree of coloring, refractive index and specific gravity of the frying oils were measured during the preparation of French fried potatoes by repeated frying. The instability of soybean oil against thermal and oxidative degradation could be lessened by using blended oils in which the ratio of palm oil to soybean oil is more than 50%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.505-508
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• 2008

In this study, temperature increase and strength development of concretes with different types of cement were investigated to construct dam drop spillway. For this purpose, boxes of 1${\times}$1${\times}$1m size with 4 different concrete mixtures were made. The types of concrete were Type I cement concrete, fly ash cement concrete and two type concrete with ternary cement, respectively. The temperature at each point were monitored in these boxes. Based on the Box test, hydration analysis of slab of 2.0m thickness was carried out. This paper presents these experimental and analytical results.

• Journal of the Society of Disaster Information
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• v.8 no.3
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• pp.204-212
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• 2012

Lightweight soils are very economical and environment friendly materials that are valuable in field without wasting construction materials, dredged soils and clay/ silty soils during construction. Recently, the research of lightweight soils mixed with recycled material (recycled tire powder, rice husks) have been investigated. In this study the mix design factors (i.e., weight of soil, water content, foaming agent and added water) were analyzed and optimized mix design was suggested using cement content for revealing strength. For the analysis the stress-strain behavior, strength with respect to time, and experimental strength for the component of recycled material were analyzed. Finally, target strength was determined to calculate reasonable and economical mix ratio and the optimized cement content was suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.189-190
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• 2010

Yeoju-Bo is a large massive concrete structures that require the reduction of working period of construction. In this study, we optimized the mix proportion of internal/external concrete and physical properties like compressive strength, semi adiabatic temperature rise in laboratory. And we also performed thermal analysis to verify the thermal cracking. Lastly we measured the hydration heat and the thermal cracking in site to verify the safety of massive concrete structure.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.181-181
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• 2011

도로는 국내 물류를 담당하는 중요한 기반시설로 국내 경제성장의 중추적인 역할을 담당하고 있다. 특히, 1970년대 개통된 경부고속도로는 우리나라의 대동맥으로 산업 성장의 파급효과를 가져오는 기반이 되었고, 공학적인 차원에서도 도로 포장재료를 경험 및 과학적으로 분석하여 적용하는 계기로 도로공학발전의 초석이 되었다. 과거에 적용된 도로 포장재료는 기술자의 경험에 의존하여 배합설계가 진행되었으며, 중차량의 비중이 많은 지역은 강성포장을 적용하고, 상대적으로 중차량이 적은 구간은 연성포장을 적용하는 설계를 따랐다. 하지만, 강성포장을 대표하는 시멘트 콘크리트 포장은 시공상의 복잡함과 시멘트 콘크리트 특성상 강도발현을 위해서 일정기간 이상의 양생일수가 필요하므로, 도로건설의 인프라 구축이 시급한 지역에서는 사용의 제약이 따른다. 연성포장을 대표적하는 재료로는 아스팔트 콘크리트 포장을 들 수 있다. 강성포장보다는 상대적으로 시공상의 편리함과 일정기간의 양생이 필요하지 않아 도로 포장재료로서 그 적용성이 우수하다. 과거에는 아스팔트 콘크리트 포장의 종류가 단순화되어 표층, 기층에 대표되는 몇몇 혼합물이 도로 포장재료로 사용되었다. 도로공학의 학문적 발달과 함께 도로포장의 전반적인 기술이 향상되고 있다. 과거의 도로 기능은 국가 경제발전을 위한 산업용 원자재의 운반이 주요 기능을 담당하고 있는 반면, 국민의 경제적 수준이 증대되고 자가용의 보급이 보편화되면서 도로 이용의 주체가 국민 개개인으로 변화되고 있고, 그 요구조건도 다양화되고 있다. 이에 발맞추어 도로공학의 기술적 향상으로 다양한 기능을 발휘할 수 있는 도로포장재료가 개발되고 있으며, 대표적인 제품으로는 배수성 포장, 반강성 포장, 보수성 포장, 탄성 포장, 저소음 포장 등이 있다. 본 연구에서는 기능성 포장의 하나인 저소음 포장의 특성 중 생산성능을 평가하였다. 생산성능이란 저소음포장을 현장 플랜트에서 생산하였을 경우의 특성을 분석하는 과정으로, 실내 실험으로 최적화된 재료의 배합은 이상적인 조건을 적용하여 결정된 것으로 입고된 현장 골재 및 생산 플랜트 조건에 따른 그 배합 및 물성이 변동을 가져올 수 있다. 특히, 저소음 포장은 기존의 아스팔트 포장과 달리 적용되는 골재, 아스팔트의 재료가 고성능을 발휘하기 위하여 특수한 재료를 적용해야 한다. 배합설계에서도 개립도 아스팔트 혼합물에 적용되는 내구성분석 절차를 따라야 하므로, 실내 배합설계 혼합물과 현장 생산 혼합물간의 물리적 특성에 차이를 나타낼 수 있다. 따라서, 본 연구에서는 실내 및 현장 혼합물의 전반적인 물리적 특성의 차이를 분석하여 저소음 포장의 현장 생산성능을 확인하였다. 분석요소로는 혼합물의 기초물성면에서는 밀도, 공극률을 분석하였으며, 실내 내구성면에서는 마샬안정도, 잔류안정도를 분석하여 실내 및 현장 혼합물의 물성차이를 분석하였다. 기초물성을 평가할 수 있는 밀도와 공극률에서는 생산 현장 혼합물이 실내 혼합물 보다 높은 밀도와 낮은 공극률을 나타내고 있으며, 이에 상관하여 강도특성을 분석할 수 있는 마샬안정도도 생산 현장 혼합물이 다소 높은 강도를 발휘하였다. 또한, 수분에 대한 안정성을 평가하는 인자인 잔류 안정도에서는 실내 및 현장 혼합물 모두 우수한 성능을 발휘하였다.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.51-60
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• 2009

This study investigates the fresh state characteristics, strength, chloride ion penetration resistance and freeze-thaw resistance of the suggested high strength-high durability cement concrete pavement. The required workability and air content could be achieved by using an appropriate admixtures. However its dosage should be carefully determined through field trial batches. Compressive strength increased with the increased cement content and, in particular, high cement volume concrete continuously developed strength up to 90 days. No clear relationship, however, existed between flexural strength and cement content. Chloride penetration resistance seemed as a function of curing age rather than the cement content. Freeze-thaw resistance test was conducted using two different coolants, tap water and 4% NaCl solution. When the tap water was used no severe damage was observed up to 300 cycles regardless the air content. Under 4% NaCl solution, specimens of 326kg/$m^3$ cement content showed severe damage with surface scaling. Based on the experimental investigations herein, it is highly recommended that the cement content be greater than 400kg/$m^3$ for strength-high durability cement concrete pavement structures.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.19-26
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• 2009

In this study, flowable backfill made with weathered granite soil is tested to provide basic engineering properties that can be used as design input to overcome settlement problems in road pavement due to low stiffness of backfill which is generated by porosity of the soil. For design purpose, a proper mixing ratio is developed first. Then several test methods including FF/RC, PMT and LDWT including axial compression test are adapted for checking stiffness and measuring axial strength of the material separately that can be used for design values.

• Elastomers and Composites
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• v.35 no.4
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• pp.261-271
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• 2000

Physical properties of NR vulcanizates cured by both sulfur and resole were studied. Cure characteristics of the compounds were also investigated. Two types of resoles with different molecular weight distributions were employed. The scorch time of the NR compound containing the resole with a low molecular weight distribution was shorter than that of the compound containing the resole with a high one. Crosslink densities of the NR vulcanizates with a high resole content after the thermal aging at $95^{\circ}C$ decreased, while that of the vulcanizate without resole after the thermal aging at $95^{\circ}C$ increased. Though crosslink densities of the NR vulcanizates with a high resole content decreased with increasing the aging time, the moduli increased while the tensile strength and tear strength decreased.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.77-85
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• 2010

Unconfined compressive strength tests were performed to evaluate curing characteristics of controlled low strength material(CLSM) made with coal ashes. It is found that unconfined compressive strength normalized by curing times, increases as decreasing the water contents of CLSM particularly during first three days. Dynamic cone penetrometer tests were also carried out to evaluate cost-effective CLSM lump strength characteristics with time. It takes around 10 days to reach target strength, 500kPa (penetration rate, 20mm/blow). Curing rate significantly decreases after 10 days elapsed regardless of CLSM formulation.